1. Field of the Invention
The present invention relates to a method and a device for holding an optical member, an optical device, an exposure apparatus, and a device manufacturing method, and more particularly, it relates to a method and a device for holding an optical member that holds an optical member such as a lens having a flange portion on the periphery portion, an optical device having a plurality of the optical members within its barrel, an exposure apparatus comprising the optical device as its optical system, and a device manufacturing method using the exposure apparatus.
2. Description of the Related Art
Conventionally, various exposure apparatus have been used in a lithographic process for producing devices such as semiconductor devices. In recent years, for example, projection exposure apparatus such as reduction projection exposure apparatus (so-called steppers) that reduce and transfer a pattern formed on a mask (also referred to as a reticle) proportionally enlarged around four to five times onto a substrate subject to exposure such as a wafer via a projection optical system based on a step-and-repeat method, or scanning projection exposure apparatus (so-called scanning steppers) that are an improvement of the steppers based on a step-and-scan method, are mainly used for producing semiconductor devices.
With these exposure apparatus, exposure wavelength has shifted to a shorter range in order to cope with finer integrated circuits and to achieve high resolution. Recently, the exposure apparatus using the ArF excimer laser which wavelength is 193 nm is in practical use, and exposure apparatus that use shorter wavelength such as the F2 laser beam (wavelength: 157 nm) or the Ar2 laser beam (wavelength: 126 nm) are also being developed.
Beams in the wavelength range called the vacuum ultraviolet that belong to the band 200 nm-120 nm, such as the ArF excimer laser beam, the F2 laser beam, or the Ar2 laser beam, have low transmittance to optical glass. Therefore, glass materials that can be used are limited to fluorite, magnesium fluoride, or fluoride crystal such as lithium fluoride. In addition, since these beams are greatly absorbed by gases such as oxygen, water vapor, and hydrocarbon gas (hereinafter referred to as xe2x80x9cadsorptive gasxe2x80x9d), it is necessary to replace gases existing on optical paths of exposure beams with gases which absorption of vacuum ultraviolet beams is low, that is, inert gas such as nitrogen or helium (hereinafter referred to as xe2x80x9clow absorptive gasxe2x80x9d as appropriate), so as to lower the concentration of the absorptive gases existing on the optical paths so that it does not exceed several ppm.
Therefore, for example, in an exposure apparatus that uses an ArF excimer laser beam as the exposure beam, in an optical system that has a relatively long optical system such as a projection optical system the interior is divided into a plurality of spaces, and each space is either filled with the low absorptive gas referred to above or a flow of the low absorptive gas is created in the space at all times.
FIG. 18 shows an example of a projection optical system used in a conventional exposure apparatus. A projection optical system PLxe2x80x2 shown in FIG. 18 comprises a double-structured barrel 350 consisting of an outer barrel 351A and inner barrels 351B1-351B4, and optical member cells C1xe2x80x2, C2xe2x80x2, C3xe2x80x2, and C4xe2x80x2 arranged within the barrel 350 at a predetermined interval along the AX direction of an optical axis. The optical member cells C1xe2x80x2, C2xe2x80x2, C3xe2x80x2, and C4xe2x80x2 are fixed on the inner circumference surface of the inner barrels 351B1, 351B2, 351B3, and 351B4, respectively.
The optical member cells C1xe2x80x2, C2xe2x80x2, C3xe2x80x2, and C4xe2x80x2 comprise lenses L1xe2x80x2, L2xe2x80x2, L3xe2x80x2, and L4xe2x80x2 serving as optical members, and lens holding devices for holding the lenses L1xe2x80x2, L2xe2x80x2, L3xe2x80x2, and L4xe2x80x2. In the space between the adjacent optical member cells, sealed chambers S1xe2x80x2, S2xe2x80x2, and S3xe2x80x2 are formed, respectively. And to each of the sealed chambers S1xe2x80x2, S2xe2x80x2, and S3xe2x80x2, gas supplying routes 330A, 330B, and 330C, and gas exhausting routes 330D, 330E, and 330F are connected, respectively, for example, so as to create a flow of the low absorptive gas at all times inside the sealed chambers S1xe2x80x2, S2xe2x80x2, and S3xe2x80x2.
FIG. 19A shows an enlarged view of an optical member cell C3xe2x80x2 in FIG. 18, while FIG. 19B shows a disassembled perspective view. As is shown in these drawings, a flange portion is provided on an outer periphery of a lens L3xe2x80x2 on its lower half portion. The lens L3xe2x80x2 is inserted from above into a hollow cylindrical lens holding metallic part 325, and the flange portion is supported from below at three points with supporting members 322a, 322b, and 322c (supporting member 322c is not shown in the drawings) which are arranged projecting from the inner circumference surface of the lens holding metallic part 325 spaced at an angle of approximately 120xc2x0. In addition, clamps 352a, 352b, and 352c (clamp 352b located in the depth of field of the drawing is not shown) are fixed to the lens holding metallic part 325 with bolts 354a, 354b, and 354c, respectively, on an upper surface of the flange portion at positions corresponding to the supporting members 322a, 322b, and 322c. So the upper surface of the flange portion is pushed downward with the clamps 352a, 352b, and 352c. 
That is, the lens L3xe2x80x2 is fixed with respect to the lens holding metallic part 325 by the flange portion provided on its outer periphery being clamped with the supporting members 322a, 322b, and 322c and the clamps 352a, 352b, and 352c. In this case, the movement of the lens L3xe2x80x2 is restricted in three degrees of freedom in the optical axis direction by the clamping force of the clamps 352a, 352b, and 352c, and the movement in the directions of the remaining three degrees of freedom is restricted by the friction between the flange portion and the supporting members and the friction between the flange portion and the clamps.
Further, the reason for employing the structure referred to above that require support at three points is because the lens, which is the object of support, can easily be attached to the lens holding metallic part and stresses due to vibration, temperature change, posture change, and the like on the lens and the lens holding metallic part can be reduced most effectively after the lens is attached, as is with the kinematic support mount which is a typical three point structure.
Incidentally, reference number 356 in FIG. 19A is a filler in order to prevent gases from flowing between the sealed chambers S2xe2x80x2 and S3xe2x80x2 arranged above and below the lens L3xe2x80x2 and to also prevent the position of the lens L3 from shifting.
The other optical member cells C1xe2x80x2, C2xe2x80x2, and C4xe2x80x2 are identically configured with the optical member cell C3xe2x80x2.
With the conventional lens holding structure described above, however, since the flange portion of the lens L3xe2x80x2 is supported at three points by the supporting members 322a, 322b, and 322c, in other words, the lens L3xe2x80x2 is not supported at points other than the three points, the periphery portion of the lens L3xe2x80x2 bends slightly in a trefoil shape (the portion not supported sags) with its own weight making the lens L3xe2x80x2 deform asymmetrically with respect to the optical axis. Furthermore, the clamping force acting on the flange portion deforms the optical surface of the lens L3xe2x80x2 via the flange portion.
So far, such deformation of the lens or the deformation of the optical surface and deterioration in the optical performance of the projection optical system caused by them has been a trivial matter. Due to higher integration of semiconductor devices, however, the performance of the projection optical system required is also becoming higher; therefore, the deformation described above can no longer be dismissed.
In addition, according to recent studies, when the gas inside the barrel of the projection optical system is replaced to an inert gas, it was discovered that the internal pressure of the barrel increases. And, when, for example, the pressure varies within the barrel, especially when the pressure differs between the adjacent sealed chambers (between rooms S1xe2x80x2 and S2xe2x80x2, and rooms S2xe2x80x2 and S3xe2x80x2 in the example described above), the situation may occur where the lens is pressurized and in some cases floats from its setting.
In actual, the projection optical system needs to withstand disturbance up to 3G in the direction within the plane perpendicular to the optical axis (lateral direction). So, for example, in order to make the friction force 3G when the coefficient of static friction xcexc is xcexc=0.2, clamping force needs to be around 15G. Under such conditions, and the lens shaped in a disk 20 mm thick with a plurality of diameters using fluorite (CaF2) as its raw material, the inventor performed a trial calculation on each the downward force, which is the sum of the clamping force and the gravitational force of the lens it self, and on the upward force caused by the pressure difference. And, by comparing both calculations, the inventor discovered that the lens is dislodged when the pressure difference reaches around 10,000 Pa.
In addition, with the conventional exposure apparatus, only the flow rate of the low absorptive gas supplied to the space within the projection optical system was different on initial gas replacement period, such as the start-up of the apparatus when gases such as air exist within the space inside the projection optical system and such internal gases have to be replaced with the low absorptive gas, and on gas purity maintenance period (steady period) when the purity of the low absorptive gas within the space needs to be maintained at a constant level after the initial gas replacement has been completed. That is, when gases were initially replaced within each inner space of the projection optical system, the flow rate of the low absorptive gas was large (for example, 50 dm3/min), and when the gas purity was maintained the flow rate of the low absorptive gas supplied to the inner space of the projection optical system was decreased compared with the initial gas replacement. Also, the same gas supplying system was used for the initial gas replacement and the gas purity maintenance described above.
Furthermore, supplying low absorptive gas to a plurality of spaces within the projection optical system was performed via a gas supplying route, which was made by opening vents in the barrel to create a gas supplying route and a gas exhausting route for each space.
By performing an experiment using equipment modeled on a projection optical system having a conventional tube-typed barrel, the inventor confirmed that the amount of light on the image plane of the projection optical system decreases with the elapse of time when the low absorptive gas is continuously purged into the inner space of the projection optical system for many hours. From this result, an assumption can be made that the transmittance decreased because impurities such as absorptive gases accumulated in the inner space of the projection optical system with the elapse of time, and light was absorbed by the impurities along the illumination optical path.
In addition, with such a purge method of low absorptive gas into the projection optical system or the like, even though the flow rate of the low absorptive gas did not have to be as large as the initial gas replacement, the purge had to be performed with a certain amount of flow of low absorptive gas in order to secure a sufficient purge performance. Therefore, when expensive gases such as helium were used as the low absorptive gas, the running cost turned out to be expensive.
Furthermore, in the case of using light which wavelength is shorter than the F2 laser beam (wavelength: 157 nm) as the illumination light for exposure, it is more likely that a reflection refraction system will be employed due to problems such as glass material or color aberration. Normally, when such a projection optical system is employed, the barrel of the projection optical system is different from that of a refraction optical system and has a barrel portion that extends in the direction intersecting the gravitational direction in addition to a barrel portion that extends in the gravitational direction. In such a case, gas flow in the inner space of the barrel portion extending in the direction intersecting the gravitational direction may become sluggish and gas may collect within the inner space of the barrel portion.
The present invention has been made in consideration of the situation described above, and has as its first object to provide a method and a device for holding an optical member that are capable of suppressing deformation of an optical member and deterioration of its optical performance to the utmost.
It is the second object of the present invention to provide an optical device that is capable of maintaining good optical performance.
It is the third object of the present invention to provide an exposure apparatus capable of performing exposure with high precision.
And, it is the forth object of the present invention to provide a device manufacturing method that can improve the productivity when producing highly integrated microdevices.
According to the first aspect of the present invention, there is provided a method for holding an optical member, the method holding the optical member via a flange portion provided on at least a part of a periphery portion close to a neutral plane position of the optical member.
With this method, the optical member is held via a flange portion provided on at least a part of a periphery portion close to a neutral plane position of the optical plane where it is free of compressive strain and tensile strain caused by the bending of the optical members. Therefore, the effect the holding force acting on the flange portion has on other portions of the optical member is suppressed to the utmost. In addition, since the neutral plane is a plane farthest from the optical surface of the optical member, the deformation of the optical surface due to the force acting on the flange portion is reduced to the minimum. Accordingly, it becomes possible to suppress the deformation of the optical surface of the optical member and deterioration in the optical properties due to the deformation to the utmost.
In this case, a plurality of points on a surface on both sides in an optical axis direction of the optical member in the flange portion can be clamped with a predetermined force.
In this case, the plurality of points can be three points that correspond to each vertex position of a triangle.
According to the second aspect of the present invention, there is provided a holding device which holds an optical member, the holding device for the optical member comprising: a holding member which one end portion in an optical axis direction of the optical member is insertable and supports a surface of a flange portion on one side in the optical axis direction in an inserted state, the flange portion provided on at least a part of a periphery portion at a center position in the optical axis direction of the optical member; and a clamping member which clamps the flange portion with the holding member by pressurizing a surface on a remaining side in the optical axis direction of the flange portion with a predetermined pressure.
With the conventional lens supporting structure previously described as a premise, according to the simulation results regarding the deformation of the optical surface of the lens (lens surface) repeatedly performed by the inventor, it has been confirmed that even with the same supporting structure the deformation of the optical surface differs depending on the thickness and the position of the flange portion, and that the deformation of the optical surface is minimized when the position of the flange portion is at the center position in the optical axis direction.
Therefore, with the present invention where the flange portion is arranged on at least a part of a periphery portion at a center position in the optical axis direction of the optical member, and the flange portion is clamped with the clamp and the holding member in a state where the flange portion is pressurized by the clamp, it becomes possible to suppress the deformation of the optical surface and the deterioration in the optical properties due to the deformation to the utmost. The following reasons can be considered for this case; that the position where the flange portion is arranged is on the periphery portion of a neutral plane where it is free of compressive strain and tensile strain caused by the bending of the optical members so that the effect the holding force acting on the flange portion has on other portions of the optical member is suppressed to the utmost, and that since the neutral plane is a plane farthest from the optical surface of the optical member, the deformation of the optical surface due to the force acting on the flange portion is reduced to the minimum.
Accordingly, the deformation occurring on the optical surface, which is the edge surfaces on both sides of the optical member in the optical axis direction, is reduced to a level that can be neglected, thus, it becomes possible to suppress the deterioration in the optical properties to the utmost.
In this case, the flange portion may be around 5 mm thick in the optical axis direction, or the flange portion may have a thickness around {fraction (1/10)} to ⅔ times as that of the peripheral edge of the portion other than the flange portion. When the thickness of the flange portion is thin, the effect the holding force acting on the flange portion has on other portions of the optical member can be suppressed, however, when it is too thin, the processing becomes difficult and also the optical member will not be able to support its own weight. And based on the results of simulations or the like performed by the inventor, with consideration of the status quo of the processing technology, it has been confirmed that both the manufacturing possibility of the optical member and the suppression of its deformation can be sufficiently satisfied when the thickness of the flange portion in the optical axis direction is around 5 mm, or around {fraction (1/10)} to ⅔ times the thickness of the peripheral edge of the portion other than the flange portion (the distance between the periphery edge on one side of the optical axis direction and the periphery edge on the other side of the optical axis direction).
According to the third aspect of the present invention, there is provided a first optical device, the device comprising: a barrel; a plurality of optical members arranged within the barrel in a predetermined positional relationship; and a holding device which holds a specific optical member via a flange portion provided on at least a part of a periphery portion close to a neutral plane position of the specific optical member, the specific optical member a part of the plurality of optical members.
With this optical device, it comprises a holding device, which holds at least a specific optical member among a plurality of optical members via a flange portion provided on at least a part of a periphery portion close to a neutral plane position of the specific optical member. Accordingly, the deformation (of the optical surface) of the specific optical member as well as the deterioration in the optical properties that occur with the elapse of time are effectively suppressed, and as a consequence, it becomes possible to maintain favorable optical properties (including image forming characteristics) for a long period of time.
In this case, the specific optical member can have the flange portion provided on at least a part of a periphery portion at a center position in an optical axis direction of the specific optical member, and the holding device can have a holding member which one end portion in an optical axis direction of the optical member is insertable and supports a surface of the flange portion on one side in the optical axis direction in an inserted state, and a clamping member which clamps the flange portion with the holding member by pressurizing a surface on a remaining side in the optical axis direction of the flange portion with a predetermined pressure.
According to the fourth aspect of the present invention, there is provided a second optical device, the device comprising: a barrel; a plurality of optical members each held in the barrel and form a plurality of sealed spaces within the barrel; a gas supply unit which supplies a specific gas into each of the sealed spaces; and a control system which controls specific gas environments in each of the sealed spaces to keep pressure difference from occurring in adjacent sealed spaces.
With this optical device, the gas supply unit supplies the specific gas into each of the plurality of sealed spaces formed by the barrel and the plurality of optical members. And upon this operation, the control system controls the specific gas environment so that pressure difference does not occur in adjacent sealed spaces. This allows the specific gas environment to be maintained without putting unnecessary pressure on the optical members. Therefore, the optical members can be kept from floating from their settings by the pressure difference and can be stably held, and damage, deformation, or the like can be effectively suppressed. This makes it possible to maintain favorable optical properties (including image forming characteristics) of the optical device. The sealed structure, in this case, may be a completely sealed structure totally cutting off outside gases, or if impurities in the outside gases do not enter the sealed space, it may be a sealed structure almost all sealed that can be maintained with a predetermined pressure.
In this case, as the control system that controls the specific gas environment, various structures can be considered. For example, the control system may include pressure sensors which measure pressure in each of the sealed spaces, and a flow amount control unit which controls the flow of the specific gas supplied into each of the sealed spaces from the gas supply unit based on measurement results of the pressure sensors, or, the control system may include a pressure adjustment unit which adjusts the internal pressure to keep pressure difference in adjacent sealed spaces from occurring in both of the adjacent sealed spaces.
In this case, various pressure adjustment units may be considered. For example, the pressure adjustment unit can be a pressure adjustment valve arranged on the partition wall of the adjacent sealed spaces, or the pressure adjustment unit can be a diaphragm arranged on the partition wall of the adjacent sealed spaces. In the former case, when pressure difference occurs in the adjacent sealed spaces, the specific gas flows from the sealed space where the pressure is high to the sealed space where the pressure is low via the pressure adjustment valve, thus automatically reducing the pressure difference in the adjacent sealed spaces to almost zero without any complicated controls. Also, in the latter case, when pressure difference occurs in the adjacent sealed spaces, due to the flexibility of the diaphragm arranged on the partition wall deforms in the direction so that the volume of the sealed space where the pressure is high increases and the volume of the sealed space where the pressure is low decreases. As a result, the pressure difference in the adjacent sealed spaces is automatically reduced or dissolved, without any complicated controls.
With the second optical device in the present invention, the specific gas can be a gas with permeability to an energy beam, and at least a part of a supply opening of the gas supply unit which supplies the specific gas into each of the sealed spaces can be arranged in a gap made between the adjacent optical members.
With the second optical device in the present invention, a flange portion can be provided on at least a part of a periphery portion close to a neutral plane position of a specific optical member, the specific optical member at least a part of specific optical members among the plurality of optical members, and the optical device can further comprise: a holding device which holds the specific optical member.
According to the fifth aspect of the present invention, there is provided a third optical device arranged on an optical path of an energy beam, the optical device comprising: a barrel; a plurality of optical members arranged in a predetermined positional relationship on the optical path of the energy beam within the barrel; a gas supply system which has a supply opening that is arranged in the barrel, and supplies a specific gas having permeability to the energy beam into a space divided by the plurality of optical members via the supply opening; an exhaust system which has an exhaust opening that is arranged in the barrel, and exhausts gas within the space via the exhaust opening; wherein the supply opening of the specific gas is arranged closer to the optical path of the energy beam than the exhaust opening of the gas.
With this optical device, the gas supply system supplies the specific gas having the properties that allow transmittance of the energy beam to the space divided by the plurality of optical members within the barrel via the supply opening arranged in the vicinity of the optical path of the energy beam. This allows the specific gas to be efficiently purged into the optical path of the energy beam and its vicinity in the space divided by the plurality of optical members within the barrel, that is, that absorptive gas or the like having the properties of absorbing the energy beam can be efficiently removed from the optical path of the energy beam and its vicinity. In addition, since the exhaust opening is arranged at a position further away from around the optical path than the supply opening of the specific gas, the amount of gas lingering within the space is reduced. Accordingly, the transmittance of the energy beam is hardly cut off by the absorptive gas or the like within the space, therefore, the energy beam transmittance of the optical device and its optical properties (including the image forming characteristics) can be favorably maintained.
As the space within the barrel divided by the plurality of optical members, the space may be formed of a completely sealed structure and completely cut off from the gases outside the space, or if it is structured so that impurities in the gases outside do not enter the space, it may be a space formed of an almost complete sealed structure which sealed state can be maintained with a predetermined pressure.
In this case, the supply opening can be arranged in a gap located between the optical members reciprocally adjacent. In such a case, the specific gas can be purged into gaps in between the optical members where it is difficult to perform a sufficient purge.
With the third optical device in the present invention, a flange portion can be provided on at least a part of a periphery portion close to a neutral plane position of a specific optical member, the specific optical member is at least one of plurality of optical members, and the optical device can further comprise: a holding device which holds the specific optical member.
With the third optical device in the present invention, a plurality of the spaces can be formed inside the barrel with the plurality of optical members, and the optical device can further comprise: a control system which controls specific gas environments in each of the sealed spaces to keep pressure difference from occurring in adjacent spaces.
According to the sixth aspect of the present invention, there is provided a fourth optical device arranged on an optical path of an energy beam, the optical device comprising: a barrel; a plurality of optical members arranged in a predetermined positional relationship on the optical path of the energy beam within the barrel; a first supplying route which is provided along with the barrel, and which has a first supply opening with a predetermined opening area for supplying a specific gas, which has permeability to the energy beam, into a space inside the barrel divided by the plurality of optical members; a second supplying route which is provided a long with the barrel, and which has a second supply opening with an opening area smaller than the first supply opening which supplies the specific gas into the space; an exhausting route which is provided along with the barrel, and which exhausts outside internal gas in the space; and a control unit which controls supply of the specific gas into the space by selecting at least one of the first supplying route and the second supplying route, depending on a state inside the space.
With this optical device, the control unit selects at least either one of the first supplying route or the second supplying route depending on the state inside the space within the barrel divided by the plurality of optical members for supplying the specific gas. That is, the specific gas is supplied to the space via the selected supplying route, and corresponding to the supply of the specific gas the internal gas within the space is exhausted outside via the exhausting route. Since the opening area is large in the first supplying route, in the case this is selected as the supplying route a large amount of the specific gas is supplied to the space. On the other hand, the opening area of the second supplying route is smaller than that of the first supplying route, so in the case this supplying route is selected a small amount of the specific gas is supplied to the space. Accordingly, by controlling the specific gas supply with the control unit selecting at least either one of the first supplying route or the second supplying route depending on the state inside the space, the gas within the space can be replaced with the specific gas in a short period of time, or, the purity of the specific gas within the space can be maintained while reducing the running cost by supplying a small amount of specific gas after the gas is replaced. Therefore, the purge performance of the optical device can be improved, and the optical properties can be favorably maintained for a long period of time.
And, as is previously described, as the space within the barrel divided by the plurality of optical members, the space may be formed of a completely sealed structure and completely cut off from the gases outside the space, or if it is structured so that impurities in the gases outside do not enter the space, it may be a space formed of an almost complete sealed structure which sealed state can be maintained with a predetermined pressure.
In this case, the control unit can replace the internal gas with the specific gas by supplying the specific gas via at least the first supplying route of the first supplying route and the second supplying route, when the internal gas of the space contains much absorptive gas which has properties of absorbing the energy beam.
In addition, the control unit can supply the space with the specific gas via the second supplying route, when the internal gas of the space contains less of absorptive gas which has properties of absorbing the energy beam.
With the fourth optical device in the present invention, the second supply opening can be arranged closer to the optical path of the energy beam than the first supply opening. In such a case, the optical path of the energy beam in the space and its vicinity can be effectively purged with the specific gas.
With the fourth optical device in the present invention, the second supply opening can be arranged in a gap located between the optical members reciprocally adjacent, and the control unit can supply the space with the specific gas via both the first and the second supplying routes, when the internal gas of the space contains much absorptive gas which has properties of absorbing the energy beam.
With the fourth optical device in the present invention, a flange portion can be provided on at least a part of a periphery portion close to a neutral plane position of a specific optical member, the specific optical member is at least one of the plurality of optical members, and the optical device can further comprise: a holding device which holds the specific optical member.
With the fourth optical device in the present invention, a plurality of spaces can be formed inside the barrel with the plurality of optical members, and the optical device can further comprise: a control system which controls specific gas environments in each of the sealed spaces to keep pressure difference from occurring in adjacent spaces.
According to the seventh aspect of the present invention, there is provided a fifth optical device arranged on an optical path of an energy beam, the optical device comprising: a first barrel portion which extends in a direction intersecting a gravitational direction, in which a first space is formed inside; a second barrel portion which is connected to the first barrel portion and extends in the gravitational direction, in which a second space is formed inside; and a first and second gas supply/exhaust systems which are arranged individually for the first space and the second space, the systems purging a specific gas having permeability to the energy beam.
With this optical device, it comprises: a first barrel portion which extends in a direction intersecting a gravitational direction, in which a first space is formed inside; a second barrel portion which is connected to the first barrel portion and extends in the gravitational direction, in which a second space is formed inside; and a first and second gas supply/exhaust systems which are arranged individually in the first space and the second space, the systems for purging a specific gas having properties that allow transmittance of the energy beam. Therefore, not only is the second space within the second barrel portion is purged with the specific gas by the second gas supply/exhaust system, but also the first space within the first barrel portion is purged with the specific gas by the first gas supply/exhaust system. Accordingly, the purge performance of the optical device can be improved by preventing the gas from lingering in the first space, thus the optical properties can be favorably maintained for a long period of time.
In this case, when the specific gas is a gas which relative density is lighter than air, gas supply openings of the first and second gas supply/exhaust systems are preferably arranged in the upper portion of the gravitational direction in each of the spaces, whereas gas exhaust openings are preferably arranged in the lower portion of the gravitational direction in each of the spaces. In such a case, when the density of the specific gas is lighter than air, each of the space is gradually filled from above with the specific gas. Therefore, with the specific gas supplied from the upper side of each space and exhausted from the lower side, the internal gas can be evenly replaced in the entire space with the specific gas.
With the fifth optical device in the present invention, the optical device can have a mirror with a first reflection surface on which the energy beam is reflected and a concave mirror which reflects the energy beam reflected off the first reflection surface onto a second surface of the mirror that are arranged in either one of the first space and the second space in any one of an individual and simultaneous manner, and in a space where the mirror is arranged, the specific gas that has a higher purity level compared with that of other spaces can be purged via a predetermined gas supply/exhaust system of the first and second gas supply/exhaust systems. In such a case, the optical path within the space including the mirror is a so-called double path optical path, thus requiring a higher purge accuracy of the specific gas compared with other portions. The space, however, is purged with the specific gas that has a higher purity than the other portions, therefore, the purge accuracy required can be sufficiently satisfied.
In this case, in the space where the mirror is arranged, a gas supply opening of the specific gas can be arranged in the vicinity of the mirror. In such a case, the mirror can be protected more effectively from deterioration due to impurities and the energy beam.
With the fifth optical device in the present invention, inside at least one of the first and the second barrel portion the optical device can comprise: a plurality of optical members arranged in a predetermined positional relationship; and a holding device which holds the specific optical member via a flange portion provided on at least a part of a periphery portion close to a neutral plane position of a specific optical member, the specific optical member is at least one of the plurality of optical members.
With the fifth optical device in the present invention, the first space and the second space can be reciprocally adjacent, and the optical device can further comprise: a control system which controls specific gas environments within each of the spaces to keep pressure difference from occurring in the first space and the second space.
With the fifth optical device in the present invention, at least one gas supply opening of the specific gas of the first and second gas supply/exhaust systems can be arranged closer to the optical path of the energy beam than a remaining gas supply opening of the specific gas.
With the fifth optical device in the present invention, at least one of the first and second gas supply/exhaust systems can have a first supplying route which has a first supply opening with a predetermined opening area for supplying a specific gas, a second supplying route which has a second supply opening with an opening area smaller than the first supply opening which supplies the specific gas, and an exhausting route which exhausts outside internal gas in a space subject to purge; and a control unit which controls supply of the specific gas into the space by selecting at least one of the first supplying route and the second supplying route, depending on a state inside the space subject to purge.
According to the eighth aspect of the present invention, there is provided a first exposure apparatus that transfers a pattern of a mask onto a substrate via a projection optical system, the exposure apparatus comprising: a first optical device in the present invention as a projection optical system.
With this exposure apparatus, the mask pattern is transferred onto the substrate via a projection optical system consisting of the optical device according to claim 7 which optical properties are favorably maintained. Therefore, the mask pattern can be transferred with high accuracy on the substrate for a long period of time, and it becomes possible to perform exposure with high precision for over a long period of time.
According to the ninth aspect of the present invention, there is provided a second exposure apparatus that illuminates a mask on which a pattern is formed with an energy beam and transfers the pattern onto a substrate via a projection optical system, the exposure apparatus comprising: a second optical device in the present invention as a projection optical system, wherein the specific gas is a gas having permeability to the energy beam.
With this exposure apparatus, since it comprises the second optical device in the present invention as the projection optical system, the optical properties of the projection optical system do not change easily with the elapse of time. Moreover, since the specific gas supplied to the sealed space within the optical system is a gas having properties of transmitting the energy beam, the energy beam entering the optical member can be maintained at a high transmittance (or reflectance), and exposure amount control with high accuracy over a long period of time becomes possible. Therefore, the mask pattern can be transferred with high accuracy on the substrate for a long period of time, and it becomes possible to perform exposure with high precision for over a long period of time.
According to the tenth aspect of the present invention, there is provided a third exposure apparatus that exposes a substrate via an optical system and a mask with an energy beam and transfers a pattern formed on the mask onto the substrate, the exposure apparatus comprising: a third optical device in the present invention arranged on an optical path of the energy beam from the mask to the substrate.
With this exposure apparatus, it comprises the third optical device in the present invention arranged on the optical path of the energy beam from the mask to the substrate, so the absorptive gas or the like having the properties of absorbing the energy beam can be efficiently removed from the optical path of the energy beam and its vicinity, and the amount of gas lingering in the space can be reduced. Accordingly, the absorptive gas or the like in the space cuts off almost none of the transmittance of the energy beam, thus, the energy beam transmittance and the optical properties of the optical device (including the image forming characteristics) can be favorably maintained. This allows exposure with high precision (transfer of the mask pattern onto the substrate) for over a long period of time. In addition, in this case, since the optical path of the energy beam and its vicinity where it greatly influences the light amount control on the substrate surface and the optical properties (including the image forming characteristics) of the optical system is effectively purged with the specific gas, the entire inner space of the optical system does not necessarily have to be purged evenly with the specific gas. Therefore, the amount of the specific gas used can be reduced, which leads to the reduction of the running cost.
As the inner space in the present invention, the space may be formed of a completely sealed structure and completely cut off from the gases outside the space, or if it is structured so that impurities in the gases outside do not enter the space, it may be a space formed of an almost complete sealed structure which sealed state can be maintained with a predetermined pressure.
In this case, the supply opening can be arranged in the gap located between said adjacent optical members. In such a case, the gap in between the optical members where it is normally difficult to perform a sufficient purge can be easily and sufficiently purged with the specific gas.
With the third exposure apparatus in the present invention, the exposure apparatus can further comprise a scanning unit that scans the mask and the substrate synchronously with respect to the energy beam during exposure of the substrate. That is, the exposure apparatus may be a scanning exposure apparatus. In such a case, the area within the optical system transmitting the energy beam is a part of the optical system (an area of a rectangular slit shape or an arcuated shape). Since, however, the optical path of the energy beam and its vicinity is purged with the specific path via the supply opening arranged close to the optical path of the energy beam, the specific gas can be purged sufficiently, regardless of the shape of the area transmitting the energy beam.
According to the eleventh aspect of the present invention, there is provided a fourth exposure apparatus that exposes a substrate via an optical system and a mask with an energy beam and transfers a pattern formed on the mask onto the substrate, the exposure apparatus comprising: a fourth optical device in the present invention as the optical system.
With this exposure apparatus, it comprises the fourth optical device in the present invention as the optical system. This allows the control system to control the specific gas supply by choosing at least either one of the first supplying route or the second supplying route depending on the state within the space divided by the plurality of optical members inside the barrel of the optical system (optical device), and as a consequence, the space can be replaced with the specific gas within a short period of time, and then the purity of the gas maintained while reducing the running cost by supplying a small amount of the specific gas into the space after the replacement. Accordingly, the purge performance of the optical device can be improved, in addition to maintaining the optical properties at a favorable level for over a long period of time. Therefore, with the present invention, the purge performance of the optical system can be improved, as well as perform exposure with high precision (transferring the mask pattern onto the substrate) for over a long period of time via the optical system that has been favorably purged.
In this case, the second supply opening can be arranged closer to the optical path of the energy beam than the first supply opening. In such a case, the optical path of the energy beam in the inner space of the optical system and its vicinity can be effectively purged with the specific gas.
With the fourth exposure apparatus of the present invention, the second supply opening can be arranged in a gap between adjacent optical elements structuring the optical system, and the control unit can supply the specific gas into the space via both the first supplying route and the second supplying route on initial gas replacement. In such a case, the gap in between the optical members where it is difficult to perform a sufficient purge on initial gas replacement can be sufficiently purged with the specific gas.
According to the twelfth aspect of the present invention, there is provided a fifth exposure apparatus that irradiates an energy beam on a mask and transfers a pattern formed on the mask onto a substrate, the exposure apparatus comprising: a fifth optical device in the present invention arranged on an optical path of the energy beam from the mask to the substrate.
With this exposure apparatus, it comprises the fifth optical device in the present invention, which is arranged on the optical path of the energy beam from the mask to the substrate. This allows not only the second space of the second barrel portion to be purged with the specific gas by the second gas supply/exhaust system, but the first space of the first barrel portion is also purged with the specific gas by the first gas supply/exhaust system. Accordingly, the gas within the first space can be kept from lingering, which improves the purge performance within the optical device, and the mask pattern can be accurately transferred onto the substrate via the optical device that has been favorably purged for over a long period of time.
In this case, the gas supply openings of the first and second gas supply/exhaust systems are preferably arranged in the upper portion of the gravitational direction in each of the spaces, whereas gas exhaust openings are preferably arranged in the lower portion of the gravitational direction in each of the spaces. In such a case, when the density of the specific gas is lighter than air, each of the space is gradually filled from above with the specific gas. Therefore, with the specific gas supplied from the upper side of each space and exhausted from the lower side, the internal gas can be evenly replaced in the entire space with the specific gas.
With the fifth exposure apparatus in the present invention, the optical device can have a mirror having a first reflection surface and a second reflection surface and a concave mirror, and the energy beam emitted from the mask can be reflected off the first reflection surface of the mirror toward the concave mirror whereas the energy beam reflected off the concave mirror can be reflected off the second reflection surface of the mirror toward the substrate, and in a space where the mirror is arranged, the specific gas that has a higher purity level compared with that of other spaces can be purged via a predetermined gas supply/exhaust system of the first and second gas supply/exhaust systems. In such a case, the optical path within the space including the mirror of the optical device becomes a so-called double path optical path, therefore, requires a purge of the specific gas with a higher accuracy compared with other portions. This space, however, is purged with a specific gas which purity is higher than that of the gas purged in the other portions, so the purge accuracy required can be sufficiently satisfied.
In addition, for example, in the case of using an F2 laser beam as the energy beam and a mirror having a reflection surface coated with metal such as aluminum as the mirror, since the reflection surface deteriorates rapidly due to the impurities within the inner space and the F2 laser beam, the present invention is effective to resolve this situation and protect the mirror.
In this case, a gas supply opening of said specific gas may be arranged in the vicinity of the mirror, in the space where the mirror is arranged. In such a case, it becomes possible to increase the efficiency in protecting the mirror from deterioration due to the impurities and the energy beam.
In addition, in the lithographic process, by using the exposure apparatus in the present invention (the first to fifth exposure apparatus) the pattern of the mask can be accurately transferred onto the substrate, therefore, microdevices with high integration can be produced with high yield and its productivity improved. Accordingly, it can be said from another aspect that the present invention is a device manufacturing method using the exposure apparatus in the present invention.